Several people in Norway said Hassan Abdi Dhuhulow was quiet and respectful at his mosque as a boy but later became angry and radicalized.

Security camera images show the 23-year-old and three other gunmen firing coldly on shoppers as they made their way along store aisles after storming the upscale mall on Sept. 21, officials said.

Until recently, investigators had referred to the attackers only by the colors of their shirts. However, two officials in Nairobi, one Western and one Kenyan, confirmed Friday to the Associated Press that one of the gunmen had been identified as Dhuhulow. The two officials insisted on anonymity because the information had not been released publicly.

The suspect's 26-year-old sister, reached in the southern Norwegian town of Larvik, said his family was unaware of any role he may have played in the four-day siege that killed at least 67 people.

"I don't want to believe this. I don't believe that this is him. It doesn't look like him. It isn't him," Idman Dhuhulow told the AP from the town of 40,000 nestled between mountains and the sea, where Dhuhulow lived after his family moved there from Somalia in 1999.

She said her brother went to the Somali capital of Mogadishu for a three-month visit in 2009, then moved to Somalia for good in March of the following year.

He had been studying economics in Norway and "his plan was to go back to Mogadishu and study there," she said.

"We had the best relationship that you can have. He was nice and careful," she said, adding that she had read media reports saying that he had become radicalized but "that's not something I saw."

Mohamed Hassan, a leader in the Somali immigrant community in Larvik, also described Dhuhulow as respectful to his elders as a young boy and a teen.

"He was a quiet, lovable boy while he was here. I never saw him fight other young boys. He was not a troublemaker here in Larvik," Hassan said.

However, others recalled a different Dhuhulow.

Bashe Musse, a Somali Norwegian community leader in Oslo, said Dhuhulow had become radicalized in the years before he left Norway. And another man, who would give only his first name, Yussuf, also said a man he believes was the Norwegian-Somali gunman was associated with radical circles in Norway. Yussuf declined to give his last name for fear of reprisals from sympathizers of al-Shabab, the Somali militant group behind the mall attack.

Al-Shabab has said the attack was in retaliation for Kenya's sending troops into Somalia to go after the extremists. Kenyan officials initially said the attack was carried out by 10 to 15 gunmen, but the security camera video shows only four. A police official said three suspects are in custody, though none directly took part in the attack.

Authorities have so far been unable to identify any of the assailants from the bodies pulled from the rubble of the mall, where a raging inferno tore through its main department store and a roof parking lot collapsed.

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